Go back a couple of pages on the forum and you'll find some very detailed build threads.
The consensus is that the basic panels fit easily enough, a little fettling is required to get a good fit. Take your time, there isn't anything difficult as such.
It does depend which kit you buy, the Z3 based Kobra and Z300 go together very quickly. You can be on the road in just a few days and be ready for paint.